Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with graphical user interface showing our new design.

In the drawing, the outermost broken line illustrates a display screen. The other broken lines illustrate portions of the graphical user interface. No subject matter depicted in the broken lines form part of the claimed design. 

CLAIM We claim the ornamental design for a display screen or portion thereof with a graphical user interface, substantially as shown and described. 